One type of vehicle occupant protection apparatus specifically increases the ability to protect the heads of the vehicle occupants when a side of the vehicle is subjected to an impact force from the outside. In this vehicle occupant protection apparatus, a folded expansion part is positioned in a location stretching from the roof of the vehicle to an upper edge of a window. The expansion part is a member capable of mitigating impact force. Side curtain airbag apparatuses are a well-known example of this type of vehicle occupant protection apparatus.
With side curtain airbag apparatuses, a side curtain airbag expands along windows, and specific components are inflated when the vehicle body has been subjected to a specific impact force. Since side curtain airbags expand in the form of a curtain, side curtain airbags can be regarded as a type of expansion part. JP-10-138857A, JP-2001-1714171A, and JP-2003-320920A are well-known examples of this type of side curtain airbag apparatus.
A summary of the technology known from JP-10-138857A will first be described based on FIG. 20 hereof.
As shown in FIG. 20, in a first conventional side curtain airbag apparatus 220 (vehicle occupant protection apparatus), a side curtain airbag 223 (expansion part), which is stored on a side edge of a roof 222 of a vehicle 221, is made to expand in the form of a curtain along a forward window 228 and a rear window 229 in the vehicle cabin A forward end of the airbag 223 is attached to a lower portion of a front pillar 225 by a forward support part 224. A rear end of the airbag 223 is attached to a rear portion of a roof rail 227 by a rear support part 226. The forward support part 224 and the rear support part 226 are positioned above a lower edge 228a of the forward window 228 and a lower edge 229a of the rear window 229.
A tension line TL joining the forward support part 224 and the rear support part 226 is a diagonal line sloping down to the front and facing the forward window 228 and the rear window 229. When expanded, the airbag 223 is in an extended state in the longitudinal direction of the vehicle 221 between the two points 224 and 226 along the tension line TL, as shown in FIG. 20.
In the expanded airbag 223, a lower half 223a, which is below the tension line TL, does not contact the vehicle body 221. Therefore, the lower half 223a slackens more readily than an upper half 223b in the widthwise direction of the vehicle.
A measure that can be conceived for addressing this problem involves increasing the tensile force for extending the airbag 223 in the longitudinal direction of the vehicle 221 in order for the vehicle occupants in the lower half 223a to be given greater protection. However, in order to increase the tensile force, a stronger structure is necessary for the forward support part 224 and the rear support part 226, which becomes a primary factor in increasing the cost and weight of the side curtain air bag apparatus 220.
Next, a summary of the technology known from JP-2001-171471A will be described with reference to FIG. 21 hereof.
As shown in FIG. 21, a second conventional side curtain airbag apparatus 230 (vehicle occupant protection apparatus) has a side curtain airbag 231 (expansion part) configured with one primary expansion part 233 and four secondary expansion parts 234 through 237. In this case, the straight line 232 extending along the lower edges of the windows of the vehicle will be referred to as the lower line 232.
In the expanded airbag 231, the primary expansion part 233 is above the lower line 232 and is elongated in the longitudinal direction of the vehicle body. The primary expansion part 233 is provided with two primary inflation parts 241, 242 for protecting the vehicle occupants. The first and second primary inflation parts 241, 242 are arranged in a row in the longitudinal direction of the vehicle.
In the expanded airbag 231, the secondary expansion parts 234 through 237 are below the lower line 232, and extend downward from the lower edge of the primary expansion part 233. The secondary expansion parts 234 through 237 are arranged in a row in the longitudinal direction of the vehicle body and are each provided with a separate secondary inflation part 244 through 247. From forward to rear, the four secondary inflation parts 244 through 247 are a first secondary inflation part 244, a second secondary inflation part 245, a third secondary inflation part 246, and a fourth secondary inflation part 247. The second secondary inflation part 245 is positioned directly below the first primary inflation part 241. The fourth secondary inflation part 247 is positioned directly below the second primary inflation part 242.
The two primary inflation parts 241, 242 and the four secondary inflation parts 244 through 247 can be inflated by gas fed from an inflator 251. The primary inflation parts 241, 242 can protect the vehicle occupants by inflating. When inflated, the secondary inflation parts 244 through 247 support the lower edge of the expanded primary expansion part 233 by contacting the inner surface of the vehicle cabin (including the inner surface of the door).
The second secondary inflation part 245 is positioned in an area near the sitting location of the forward vehicle occupant. The fourth secondary inflation part 247 is positioned in an area near the sitting location of a rear vehicle occupant. When the airbag 231 expands, the second and fourth secondary inflation parts 245, 247 must quickly inflate and enter the space between the lateral surface of the vehicle cabin and the vehicle occupants in the front and rear. A vehicle occupant may, for example, come into contact with the expanded second secondary inflation part 245 before the secondary inflation part 245 has inflated. In such instances it is difficult for the second secondary inflation part 245 to fully expand.
A measure that can be conceived for addressing this problem involves increasing the flow rate of gas produced by the inflator 251 so that the second and fourth secondary inflation parts 245, 247 will inflate more quickly in order to increase the ability with which the vehicle occupants will be protected by the airbag 231. However, the inflator 251 will be larger, which becomes a primary factor in increasing the cost and weight of the side curtain airbag apparatus 230.
Next, a summary of the technology known from JP-2003-320920A will be described with reference to FIG. 22 hereof.
As shown in FIG. 22, a third conventional side curtain airbag apparatus 240 (vehicle occupant protection apparatus) has a side curtain airbag 241 (expansion part) provided with two primary inflation parts 242, 243 and two secondary inflation parts 244, 245.
The first and second primary inflation parts 242, 243 are arranged in a row in the longitudinal direction of the vehicle body and are inflated by gas fed from an inflator, absorbing the impact received by the vehicle occupants.
The first secondary inflation part 244 adjusts the internal pressure of the first primary inflation part 242 and is positioned adjacent to the first primary inflation part 242. A first break part 246, which can be broken by the internal pressure of the first primary inflation part 242, forms a partition between the first primary inflation part 242 and the first secondary inflation part 244.
The second secondary inflation part 245 adjusts the internal pressure of the second primary inflation part 243 and is positioned adjacent to the second primary inflation part 243. A second break part 247, which can be broken by the internal pressure of the second primary inflation part 243, forms a partition between the second primary inflation part 243 and the second secondary inflation part 245.
For example, the first break part 246 breaks when the internal pressure of the first primary inflation part 242 exceeds a reference pressure through contact made between a vehicle occupant and the inflated first primary inflation part 242. The space between the first primary inflation part 242 and the first secondary inflation part 244 will suddenly open as a result. At this point, the gas within the first primary inflation part 242 flows into the first secondary inflation part 244 all at once. The pressure within the first primary inflation part 242 immediately decreases.
The internal pressure of the first primary inflation part 242 can preferably be kept at a specific pressure for a specific period of time in order to increase the ability to protect the vehicle occupants with the airbag 241 when the side of the vehicle is subjected to an impact force. In this way, the impact received by the vehicle occupants can be adequately absorbed.
Accordingly, a demand exists for a technique that can achieve a lighter, less expensive vehicle occupant protection apparatus while increasing the ability of the vehicle occupant protection apparatus to protect the vehicle occupants.